Adding more fiber to your diet is an easy way to stay lean, especially during the winter months when calories consumed can outnumber calories burned on the bike, says Amy Jamieson-Petonic, RD, director of wellness coaching at the Cleveland Clinic and a spokesperson for the American Dietetic Association.

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Fiber swells in the stomach and intestinal tract, which helps you feel fuller longer, so you eat less. Tufts University researchers found that adding 14 grams of fiber a day to their diets helped people eat about 10 percent fewer calories and lose five pounds over four months. And a 2008 study at Penn State University found that people who put more broccoli and less roast beef and rice on their dinner plate consumed up to 86 fewer calories—but felt just as full. "The increased fiber and water content curbs people's hunger," says Jennifer Meengs, RD, one of the study's authors.

Fiber is the indigestible part of plants: It travels through the digestive system intact and flushes out the plumbing "like nature's scrub brush," says Jamieson-Petonic. But beyond keeping you regular, fiber-rich fruits and vegetables often contain vitamins and minerals that cyclists need for energy and recovery. By targeting fiber, you're indirectly upping your nutrient density, Jamieson-Petonic says. "Plus, research indicates that a high-fiber diet reduces your risk for cardiovascular disease, cancer and diabetes," she says.

But don't overdo it. Experts recommend 25 to 38 grams of fiber per day—any more and you'll likely experience excessive gas and undesirably urgent movements. To avoid such discomforts, Jamieson-Petonic recommends cyclists gradually increase their fiber intake while also increasing water consumption. "Fiber draws water from the intestinal lining, so you'll need additional fluids to help move things along," she says.

A Question of Timing
Fiber's filling properties are great—except when you're sprinting or cranking up a hill. That's when you want ready fuel, not bulk that cuts down on how fast you can tap into food's energy. "Fiber slows digestion and the release of sugar into the system," says Coni Francis, RD, senior manager for scientific and government affairs at GTC Nutrition. That's why high-fiber foods tend to score low on the glycemic index (GI).

So low-GI foods that are high in fiber (like beans, apples and whole grains) aren't a smart fuel choice during your ride. It's also best to limit fiber right afterward, when recovering muscles require the immediate replenishment of high-GI foods. Instead, eat fiber-rich carbohydrates (such as rolled oats or brown rice) before your workout: They'll provide sustained energy and keep you from bonking. "Fiber spares your glycogen stores for as long as possible to help you get through your ride," says Jamieson-Petonic. And enjoy fiber-rich fruits and vegetables as snacks and additions to regular meals.